Table 7.

Total Yields (Percent of Starting Material Converted into Products) and Product Branching Ratios in Methanol/Water After Ultraviolet Photolysis for 30 minutes

EA of radical sitea(eV)	0.99		0.93		0.32
PA (kcal/mol)b	219.6		218.5		212.2
EA (eV) of radical site after protonationa	5.84		6.08		6.59
Estimated pKacof the iodopyridine precursor	2.9		2.3		1.1
Branching ratios of reaction products and reaction yields (%)	pH 1.0d		pH 1.1		pH 1.0
	H abs.	100%	H abs.	100%	H abs.	33%
					Hydroxyl abs.	36%
					Methoxyl abs.	31%
	Yield	44%	Yield	43%	Yield	23%
	pH 1.7		pH 1.7		pH 1.6
	H abs.	100%	H abs.	100%	H abs.	28%
					Hydroxyl abs.	39%
					Methoxyl abs.	33%
	Yield	40%	Yield	38%	Yield	19%
	pH 2.2		pH 2.4		pH 2.2
	H abs.	100%	H abs.	100%	H abs.	31%
					Hydroxyl abs.	34%
					Methoxyl abs.	35%
	Yield	40%	Yield	31%	Yield	22%
	pH 3.1		pH 3.1		pH 2.7
	H abs.	100%	H abs.	100%	H abs.	29%
					Hydroxyl abs.	36%
					Methoxyl abs.	35%
	Yield	38%	Yield	25%	Yield	19%

^aCalculated at the (U)BLYP/aug-cc-pVDZ//(U)BLYP/cc-pVDZ level of theory.

^bCalculated at the RHF-UCCSD(T)/cc-pVTZ//UBPW91/cc-pVDZ level of theory by using an isodesmic reaction involving pyridine as the reference base; corrected for zero-point vibrational energy differences at 298 K by using the (unscaled) UBPW91/cc-pVDZ frequencies.

^cThe pKa values were reported previously as measured in a mixture of water and ethanol (1:1, v/v). See Reference 37.

^dThe pH of the reaction mixtures was adjusted by using a solution containing a mixture of HCl and KCl.